So I got 4.5.1 up and mostly running on a FC6 i386 box. The mail client seems to work fine for the admin user that was created during the install, however getting to the administration application on port 7071 fails. I can see that there is a tomcat process listening on that port (via lsof) and the firewall is open for that port. However, when I load the url for http://myserver:7071/ all I get is a 7 byte binary reply which Firefox just saves as a file.
Loading Zimbra writes a "/opt/zimbra/tomcat/logs/stacktrace.(number)" file, so presumably Tomcat is loading but the application isn't loading fully. The stack trace file is 82K (and exceeds the forum file limit). The catalina.out file has the occasional line "[tomcat launcher] got signal SIGTERM invoking stop". Other than that though I'm not sure what's going on exactly.